(1) Field of the Invention
The present invention relates to a resin composition having a superior shapability and a shaped article obtained therefrom. More particularly, it relates to a resin composition which can be stably shaped over a long time by the melt extrusion method without an occurrence of gelation or other problems, and to a resin shaped article, such as a sheet or a film, obtained by melt-extruding this resin composition.
A resin composition comprising a saponified ethylene/vinyl acetate copolymer and a polyamide is provided with the high oxygen gas barrier property and high oil resistance characteristic of the saponified ethylene/vinyl acetate copolymer and the high strength and toughness characteristic of the polyamide, and this composition is highly transparent. Accordingly, this composition has attracted attention as a material for a food-packaging film or sheet and vessels used for various purposes, and the development of compositions of this type is underway.
2) Description of the Related Art
For example, Japanese Examined Patent Publication No. 44-24277 discloses the preparation of a film from a resin composition comprising a saponified ethylene/vinyl acetate copolymer having an ethylene content of 10 to 58 mole % and a saponification degree of at least 90 mole % and a polyamide, and Japanese Unexamined Patent Publication No. 54-16576 discloses the preparation of a film from a resin composition obtained by blending a saponified ethylene/vinyl acetate copolymer having an ethylene content of 20 to 45 mole % and a saponification degree of at least 95% with a polyamide resin having a melting point of 90.degree. to 180.degree. C.
These resin compositions, however, do not have a good processability, and therefore, cannot be regarded as having a high practical utility. More specifically, when a melt extrusion of these resin compositions is continuously carried out for a long time, a gel is formed in the melt and the gel is accumulated in a screw zone of an extruder or an extruding zone of a die, resulting in a lowering of the physical properties of the obtained shaped article, and if the formation of a gel is serious, a screen or nozzle of an extruder becomes clogged, and it is necessary to at once stop the operation, disassemble the extruder, remove the clogging substances, and restart the operation. Namely, the long-run property during melt extrusion is poor.
To solve this problem, Japanese Unexamined Patent Publication No. 62-7761 proposes a mixed resin composition comprising an .alpha.-olefin type ionomer resin as a third component, and Japanese Unexamined Patent Publication No. 62-106994 proposes a resin composition comprising a polyamide resin in which the contents of the terminal carboxyl group and terminal amino group satisfy a requirement represented by a specific relational expression.
Nevertheless, these resin compositions are unsatisfactory in that, in the former resin composition, the mixing ratios of the respective components are limited within very narrow ranges, and outside these ranges, the obtained shaped article becomes hazy. Furthermore, in the latter resin composition, it has been found that, when the melt extrusion processing is conducted for a long time, the formation of a gel cannot be avoided.
Moreover, even though the formation of a gel is not serious enough to clog the screw or nozzle of the extruder, surface roughening of an obtained shaped article such as a sheet or film occurs, and breaking occurs at the gelled portion at the drawing step or the step of heat-setting the drawn product. Namely, these resin compositions have a poor long-run property for a melt extrusion processing.